Extracorporeal Membrane Oxygenation (ECMO)

Also known as ECMO · Extracorporeal life support · VV ECMO · VA ECMO · ECLA · Extracorporeal CO2 removal

Extracorporeal membrane oxygenation (ECMO) is the ultimate respiratory and circulatory support — a pump and an oxygenator outside the body that replace the lung (the venovenous, VV ECMO) or the heart and the lung (the venoarterial, VA ECMO). This topic builds the examiner's framework on the circuit and the cannulation, the two modes (VV for the isolated respiratory failure, VA for the cardiogenic shock and the arrest), the evidence (the EOLIA trial for the severe ARDS, the CESAR trial for the conventional-vs-ECMO, and the VA ECMO complications), the anticoagulation and the complications (the bleeding, the thrombosis, the haemolysis, the infection, the limb ischaemia), the weaning and the decannulation, and the ethical and the resource questions of the ECMO.

medium21 referencesUpdated 20 Aug 202635 min readVerification in progress

Practise this topic

8 MCQs

The one-line answer

ECMO is the external pump and oxygenator that replaces the lung (VV ECMO, for severe refractory respiratory failure) or the heart and lung together (VA ECMO, for refractory cardiogenic shock and arrest). The modern VV threshold is the EOLIA entry criteria — PaO2/FiO2 under 50 for more than 3 h, under 80 for more than 6 h, or pH under 7.25 with PaCO2 at or above 60 mmHg for more than 6 h, on optimised conventional ventilation. EOLIA (NEJM 2018) was stopped early at the interim analysis with no significant 60-day mortality difference (35 versus 46 per cent), but a Bayesian reanalysis put the probability of mortality benefit at 88–99 per cent across prior assumptions, and the CESAR–EOLIA individual-patient-data meta-analysis found lower 90-day mortality with ECMO (RR 0.75); CESAR (Lancet 2009) established the regional ECMO referral model. Anticoagulation is unfractionated heparin, most commonly monitored with the aPTT, balanced against bleeding — at least one bleeding event occurs in about half of VV patients (PROTECMO, 52.5 per cent). VV is weaned by the sweep-off trial, VA by the flow-reduction trial. The mantra: ECMO is a bridge to recovery, to decision, or to a durable therapy — never a destination.^[1]^[2]^[14]^[15]^[17]

Meet the patient

A 45-year-old previously well man is seven days into influenza A pneumonia, intubated and ventilated with ARDS. Despite prone positioning for sixteen hours, neuromuscular blockade, tidal volume 6 mL/kg PBW, PEEP 14, and FiO2 1.0, his blood gas — unchanged for the last eight hours — is PaO2 56 mmHg, PaCO2 62 mmHg, pH 7.18. His plateau pressure is 36 cmH2O at a reduced tidal volume of 4 mL/kg, his driving pressure is above 18, and his nurses are asking why the SpO2 will not climb. He meets the EOLIA criteria (PaO2/FiO2 under 80 and pH under 7.25 with PaCO2 above 60, both sustained for more than six hours), his lungs need to rest, and the tertiary centre is two hours away.^[1]^[12]

The two questions that decide his next twelve hours: can the lungs recover if we let them rest? (the EOLIA question — yes, often) and can we get him there safely? (the transfer question — high-risk in a hypoxic, hypercapnic, acidotic patient on extreme ventilator settings). Hold both questions and the rest of this topic slots into place.^[1]

References21Show

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[2]Peek GJ, Mugford M, Tiruvoipati R, et al.; CESAR trial collaboration. Efficacy and economic assessment of conventional ventilatory support versus extracorporeal membrane oxygenation for severe adult respiratory failure (CESAR). Lancet, 2009.PMID 19762075
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